This invention relates to a jet propulsion system for a watercraft and more particularly to an improved sound deadening arrangement for watercraft jet propulsion units.
Jet propulsion units are becoming particularly popular as propulsion units for watercraft, Jet propulsion units are quite desirable for use in a particular type of small watercraft that is designed to be operated by only one rider either alone or with a small number of passengers. With such watercraft, the jet propulsion unit is normally positioned in a tunnel formed beneath the hull and which tunnel is juxtaposed to the passenger compartment.
As is well known, jet propulsion units for watercraft include a water inlet portion that forms a duct through which water is drawn from the body of water in which the watercraft is operating. This water is drawn by an impeller which is positioned to the rear of the water inlet duct and which is driven by a powering internal combustion engine. The water is then discharged rearwardly through a discharge nozzle under the action of the impeller for propelling the associated watercraft.
Although this type of propulsion unit has a number of advantages, the flow of water through the inlet duct is not uniform and pulsations occur due to the fact that the impeller has a number of individual blades, Although the effects of pulsations can be reduced by increasing the number of blades, an increasing number of blades can reduce the pumping efficiency. The pulsations which occur in the water in the inlet portion are transmitted through the housing of the jet propulsion unit to the passenger compartment of the associated vehicle and this is obviously objectionable.
It is, therefore, a principal object of this invention to provide an improved jet propulsion unit for a watercraft that will reduce the sound transmission.
It is a further object of this invention to provide an improved arrangement for deadening the sound in the water inlet portion of a watercraft jet propulsion unit.
It is a further object of this invention to provide an improved sound deadening arrangement for the water inlet portion of such a jet propulsion unit.